High-throughput screen for FDA approved drugs that amplify Beta-cell mass in vivo The aim of the project proposed here is to identify drugs that will be therapeutic in the treatment of Diabetes. Type I (or Juvenile) Diabetes is caused by a chronic loss of the insulin-producing [unreadable]-cells of the pancreas. Without insulin the body fails to regulate blood glucose levels leading to adverse pathology. There is a high degree of conservation in the molecular mechanisms that control vertebrate pancreas development;therefore, we have turned to the zebrafish as an alternative model system to study [unreadable]-cell biology. As zebrafish larvae are small, and fit inside single wells of multiwell plates, they are the only vertebrate model system suited for carrying out high-throughput chemical screens. One of the largest problems in finding new therapeutic drugs is the huge lag between discovery and getting the drug into the clinic. To expedite this process, we use two approaches: 1) drugs are tested directly in animal models, and 2) the compound library we are screening - the Johns Hopkins Drug Library (JHDL) - is a unique resource of mainly FDA approved drugs. Thus, regardless of current use, any FDA drug found to be therapeutic in our research will have a significantly faster route into the clinic, and human trials. Our published work has shown that [unreadable]-cell formation in the secondary islets of fish pancreata is functionally equivalent to [unreadable]-cell neogenesis in mammals. Hence, drugs that cause early differentiation of [unreadable]-cells in fish larvae are hypothesized to also induce [unreadable]-cell neogenesis in mammals. Using transgenic zebrafish we performed a drug screen for inducers of precocious [unreadable]-cell formation. From 3347 drugs evaluated we identified 5 'Hits'. As part of this proposal, we plan to validate these 'Hit'compounds in murine models of Type I diabetes. Furthermore, we intend to reinvestigate the JHDL to search for compounds that function at concentrations not tested in our initial screen, and to test promising leads in synergistic combinations. Finally, we will develop the tools for a second screen. This follow-up screen will again use transgenic zebrafish but will be aimed at identifying compounds that induce proliferation of endogenous [unreadable]-cells. Between our 2 screens we aim to find compounds that induce [unreadable]-cell formation and increase their continued production. In this way we hope to find FDA approved drugs that will increase [unreadable]-cell mass in humans and that will be therapeutic in the treatment of diabetes. We also intend to use our knowledge of [unreadable]-cell biology to elucidate the mode of action of the drugs we identify. This will further our understanding of [unreadable]-cell neogenesis and reveal molecular pathways that could be exploited to develop better therapies. The methods and technologies we have developed for our screening are universal in nature, being based on relative expression levels of reporter proteins. Thus, these techniques will be of considerable interest to researchers investigating a wide array of human diseases. PUBLIC HEALTH RELEVANCE: High-throughput screen for FDA approved drugs that amplify Beta-cell mass in vivo In an effort to find therapies for diabetes, we have just finished an innovative high-throughput screen on larval zebrafish. We screened a library of FDA approved drugs for compounds that cause differentiation of [unreadable]-cells. By validating the drugs most effective at inducing [unreadable]-cell formation from our initial screen and drugs that induce proliferation in our proposed second screen, ultimately we aim to find drugs that can increase [unreadable]-cell mass in humans.